1. Field of the Invention
The present invention relates to a method and apparatus for cleaning the atmosphere; and more particularly to a stationary substrate such as a stationary motor vehicle comprising at least one atmosphere contacting surface having a pollution treating composition thereon.
2. Discussion of the Related Art
A review of literature relating to pollution control reveals that the general approach is to reactively clean waste streams entering the environment. If too much of one pollutant or another is detected or being discharged, the tendency has been to focus on the source of the pollutant, the cause of the pollutant or the waste stream containing the pollutant. For the most part gaseous streams are treated to reduce the pollutants prior to entering the atmosphere.
It has been disclosed to treat atmospheric air directed into a confined space to remove undesirable components therein. However, there has been little effort to treat pollutants which are already in the environment; the environment has been left to its own self cleansing systems.
References are known which disclose proactively cleaning the environment. U.S. Pat. No. 3,738,088 discloses an air filtering assembly for cleaning pollution from the ambient air by utilizing a vehicle as a mobile cleaning device. A variety of elements are disclosed to be used in combination with a vehicle to clean the ambient air as the vehicle is driven through the environment. In particular, there is disclosed ducting to control air stream velocity and direct the air to various filter means. The filter means can include filters and electronic precipitators. Catalyzed postfilters are disclosed to be useful to treat nonparticulate or aerosol pollution such as carbon monoxide, unburned hydrocarbons, nitrous oxide and/or sulfur oxides, and the like.
Another approach is disclosed in U.S. Pat. No. 5,147,429. There is disclosed a mobile airborne air cleaning station. In particular this patent features a dirigible for collecting air. The dirigible has a plurality of different types of air cleaning devices contained therein. The air cleaning devices disclosed include wet scrubbers, filtration machines, and cyclonic spray scrubbers.
The difficulty with devices disclosed to proactively clean the atmospheric air is that they require new and additional equipment. Even the modified vehicle disclosed in U.S. Pat. No. 3,738,088 requires ducting and filters which can include catalytic filters.
DE 40 07 965 C2 to Klaus Hager discloses a catalyst comprising copper oxides for converting ozone and a mixture of copper oxides and manganese oxides for converting carbon monoxide. The catalyst can be applied as a coating to a self heating radiator, oil coolers or charged-air coolers. The catalyst coating comprises heat resistant binders which are also gas permeable. It is indicated that the copper oxides and manganese oxides are widely used in gas mask filters and have the disadvantage of being poisoned by water vapor. However, the heating of the surfaces of the automobile during operation evaporates the water. In this way, continuous use of the catalyst is possible since no drying agent is necessary.
Responsive to the difficulties associated with devices for proactively treating the atmosphere, the Assignee herein in U.S. patent application Ser. No. 08/589,182 filed on Jan. 19, 1996, now abandoned, incorporated herein by reference, disclosed apparatus and related methods for treating the atmosphere by employing a moving vehicle. In preferred embodiments a portion of the cooling system (e.g., the radiator) is coated with a catalytic or adsorption composition. Additionally, a fan associated with the cooling system can operate to draw or force air into operative contact with the radiator. Pollutants contained within the air such as ozone and/or carbon monoxide and/or hydrocarbons are then converted to non-polluting compounds (e.g., oxygen gas, carbon dioxide and water).
While this system is effective for reducing or eliminating pollution by the use of moving vehicles, it should be noted that only about 10% of all motor vehicles are moving during peak pollution periods, typically from about noon to 6 p.m. for ozone. Ozone is generated in highest concentrations during the hottest part of the day. In large cities such as Los Angeles, New York and the like the afternoon hours represent the periods of highest ozone concentration. Yet if only 10% of all motor vehicles are moving during this period of time, then the remaining 90% of the motor vehicles are idle and cannot avail themselves of the pollution eliminating benefits described in U.S. patent application Ser. No. 08/589,182 filed on Jan. 19, 1996.
It would therefore be a significant advance in the art of treating the atmosphere to remove pollutants if stationary devices such as billboards, air conditioners, non-moving motor vehicles and the like equipped with a pollution removing composition, can be used to treat air to remove pollutants therefrom. In particular, it would be of significant benefit to employ the tremendous numbers of idle motor vehicles as air treating devices to reduce pollution and smog, particularly in large cities.
The present invention relates to an apparatus and method to treat the atmosphere to remove pollutants therefrom. The term xe2x80x9catmospherexe2x80x9d is defined herein as the mass of air surrounding the earth. The term xe2x80x9cambient airxe2x80x9d shall mean the atmosphere which is drawn or forced towards the substrate. It is intended to include air which has been heated either incidentally or by a heating means.
The present invention is generally directed to a method for treating the atmosphere comprising passing ambient air over a stationary substrate having at least one air contacting surface having a pollutant treating composition thereon. The stationary substrate is any substrate that can be modified by coating, for example, to contain the pollutant treating composition. In a preferred form of the invention, the stationary substrate is associated with a motor vehicle at rest with the engine shut off.
The ambient air is drawn over the substrate by natural wind currents or preferably by the use of an air drawing means such as a fan or the like to draw or force ambient air into operative contact with the substrate having the pollution treating composition thereon. By way of example, the fan may be positioned in a tunnel, or as part of an air conditioning system or a fan, preferably in motor vehicles a standard fan, used in a conventional cooling system of a motor vehicle. The fan is typically operated by a power source such as a battery, preferably the conventional 12 volt battery used in a motor vehicle, solar panel and the like.
The present invention is devised to operate in response to the presence of pollutants in the atmosphere. Accordingly, the present invention may be provided with a sensor adapted to detect levels of selected pollutants such as ozone. At various locations, such as certain urban areas (i.e. Los Angeles) one pollutant, ozone is present at peak levels during the early afternoon hours (i.e., noon to 6 p.m.).
Alternatively, the fan or other air drawing or forced air device may be activated once the temperature of the ambient air reaches a predetermined minimum level (e.g., 85xc2x0 F.). Temperature may be used as an indication of the presence of ozone. This is because it is known that on hot days, the level of ozone is at its highest. Accordingly, a temperature sensor may be used to activate the power source when the temperature reaches a predetermined minimum (e.g., 85xc2x0 F.).
If the power source is drained or cannot sustain the voltage necessary to drive the air drawing device without interfering with the power source""s ability to start the vehicle, it is desirable to override the system. In this way, the air drawing device is not activated or is deactivated even if the ambient air contains the minimum concentration of pollutants and/or is at the minimum required temperature. Accordingly, the present invention can be provided with a power level detecting device or sensor which detects the level of power available from the power source and compares the available power with a predetermined power level sufficient to operate the air drawing device and allow easy starting of the vehicle.
In another aspect of the present invention there may be provided a timing device which serves to activate the air drawing device for a preselected amount of time and/or a predetermined period of time when the vehicle is not in operation. It should be understood that the system of the present invention is deactivated when the engine of a motor vehicle is operating.
The present invention is also applicable to conditions where the ambient air is heated by a heater or by incidental contact with a heated object such as a motor vehicle radiator or engine which has not yet cooled to ambient temperatures or by other means such as a heat exchanger. Elevating the temperature of the ambient air makes it possible to convert additional pollutants (e.g., carbon monoxide) to non-polluting compounds (e.g., carbon dioxide).
The present invention is directed to compositions, methods and articles to treat pollutants in air. Such pollutants may typically comprise from 0 to 400 parts, more typically 1 to 300, and yet more typically 1 to 200, parts per billion (ppb) ozone; 0 to 30 parts, and more typically 1 to 20, parts per million (ppm) carbon monoxide; and 2 to 3000 ppb unsaturated hydrocarbon compounds such as C2 to about C20 olefins and partially oxygenated hydrocarbons such as alcohols, aldehydes, esters, ethers, ketones and the like. Typical hydrocarbons which can be treated include, but are not limited to, propylene, butylene, formaldehyde and other airborne hydrocarbon gases and vapors. Other pollutants present may include nitrogen oxides and sulfur oxides. The National Ambient Air Quality Standard for ozone is 120 ppb, and for carbon monoxide is 9 ppm.
Pollutant treating compositions include catalyst compositions useful for catalyzing the conversion of pollutants present in the atmosphere to non-objectionable materials. Alternatively, adsorption compositions can be used as the pollutant treating composition to adsorb pollutants which can be destroyed upon adsorption, or stored for further treatment at a later time.
Catalyst compositions can be used which can assist in the conversion of the pollutants to harmless compounds or to less harmful compounds. Useful and preferred catalyst compositions include compositions which catalyze the reaction of ozone to form oxygen, catalyze the reaction of carbon monoxide to form carbon dioxide, and/or catalyze the reaction of hydrocarbons to form water and carbon dioxide. Specific and preferred catalysts to catalyze the reaction of hydrocarbons are useful for catalyzing the reaction of low molecular weight unsaturated hydrocarbons having from two to twenty carbons and at least one double bond, such as C2 to about C8 mono-olefins. Such low molecular weight hydrocarbons have been identified as being sufficiently reactive to cause smog. Particular olefins which can be reacted include propylene and butylene. A useful and preferred catalyst can catalyze the reactions of both ozone and carbon monoxide; and preferably ozone, carbon monoxide and hydrocarbons.
Ozonexe2x80x94Useful and preferred catalyst compositions to treat ozone include a composition comprising manganese compounds including oxides such as Mn2O3 and MnO2 with a preferred composition comprising xcex1-MnO2, and cryptomelane being most preferred. Other useful and preferred compositions include a mixture of MnO2 and CuO. Specific and preferred compositions comprise hopcalite which contains CuO and MnO2 and, more preferably CARULITE(copyright) catalyst which contains MnO2, CuO and Al2O3 and sold by the Carus Chemical Co. An alternative composition comprises a refractory metal oxide support on which is dispersed a catalytically effective amount of a palladium component and preferably also includes a manganese component. Also useful is a catalyst comprising a precious metal component, preferably a platinum component on a support of coprecipitated zirconia and manganese oxide. The use of this coprecipitated support has been found to be particularly effective to enable a platinum component to be used to treat ozone. Yet another composition which can result in the conversion of ozone to oxygen comprises carbon, and palladium or platinum supported on carbon, manganese dioxide, CARULITE(copyright) catalyst and/or hopcalite. Manganese supported on a refractory oxide such as alumina has also been found to be useful.
Carbon Monoxidexe2x80x94Useful and preferred catalyst compositions to treat carbon monoxide include a composition comprising a refractory metal oxide support on which is dispersed a catalytically effective amount of a platinum or palladium component, preferably a platinum component. A most preferred catalyst composition to treat carbon monoxide comprises a reduced platinum group component supported on a refractory metal oxide, preferably titania. Useful catalytic materials include precious metal components including platinum group components which include the metals and their compounds. Such metals can be selected from platinum, palladium, rhodium and ruthenium, gold and/or silver components. Platinum will also result in the catalytic reaction of ozone. Also useful is a catalyst comprising a precious metal component, preferably a platinum component on a support of coprecipitated zirconia and manganese dioxide. Preferably, this catalyst embodiment is reduced. Other useful compositions which can convert carbon monoxide to carbon dioxide include a platinum component supported on carbon or a support comprising manganese dioxide. Preferred catalysts to treat such pollutants are reduced. Another composition useful to treat carbon monoxide comprises a platinum group metal component, preferably a platinum component, a refractory oxide support, preferably alumina and titania and at least one metal component selected from a tungsten component and rhenium component, preferably in the metal oxide form.
Hydrocarbonsxe2x80x94Useful and preferred catalyst compositions to treat unsaturated hydrocarbons including C2 to about C20 olefins and typically C2 to C8 mono-olefins such as propylene and partially oxygenated hydrocarbons as recited have been found to be the same type as recited for use in catalyzing the reaction of carbon monoxide with the preferred compositions for unsaturated hydrocarbons comprising a reduced platinum component and a refractory metal oxide support for the platinum component. A preferred refractory metal oxide support is titania. Other useful compositions which can convert hydrocarbons to carbon dioxide and water include a platinum component supported on carbon or a support comprising manganese dioxide. Preferred catalysts to treat such pollutants are reduced. Another composition useful to convert hydrocarbons comprises a platinum group metal component, preferably a platinum component, a refractory oxide support, preferably alumina and titania and at least one metal component selected from a tungsten component and rhenium component, preferably in the metal oxide form.
Ozone and Carbon Monoxidexe2x80x94A useful and preferred catalyst which can treat both ozone and carbon monoxide comprises a support such as a refractory metal oxide support on which is dispersed a precious metal component. The refractory oxide support can comprise a support component selected from the group consisting of ceria, alumina, silica, titania, zirconia, and mixtures thereof. Also useful as a support for precious metal catalyst components is a coprecipitate of zirconia and manganese oxides. Most preferably, this support is used with a platinum component and the catalyst is in reduced form. This single catalyst has been found to effectively treat both ozone and carbon monoxide. Other useful and preferred precious metal components are comprised of precious metal components selected from palladium and also platinum components with palladium preferred. A combination of a ceria support with a palladium component results in an effective catalyst for treating both ozone and carbon monoxide. Other useful and preferred catalysts to treat both ozone and carbon monoxide include a platinum group component, preferably a platinum component or palladium component and more preferably a platinum component, on titania or on a combination of zirconia and silica. Other useful compositions which can convert ozone to oxygen and carbon monoxide to carbon dioxide include a platinum component supported on carbon or on a support comprising manganese dioxide. Preferred catalysts are reduced.
Ozone, Carbon Monoxide and Hydrocarbonsxe2x80x94A useful and preferred catalyst which can treat ozone, carbon monoxide and hydrocarbons, typically low molecular weight olefins (C2 to about C20) and typically C2 to C8 mono-olefins and partially oxygenated hydrocarbons as recited comprises a support, preferably a refractory metal oxide support on which is dispersed a precious metal component. The refractory metal oxide support can comprise a support component selected from the group consisting of ceria, alumina, titania, zirconia and mixtures thereof with titania most preferred. Useful and preferred precious metal components are comprised of precious metal components selected from platinum group components including palladium and platinum components with platinum most preferred. It has been found that a combination of a titania support with a platinum component results in the most effective catalyst for treating ozone, carbon monoxide and low molecular weight gaseous olefin compounds. It is preferred to reduce the platinum group components with a suitable reducing agent. Other useful compositions which can convert ozone to oxygen, carbon monoxide to carbon dioxide, and hydrocarbons to carbon dioxide include a platinum component supported on carbon, a support comprising manganese dioxide, or a support comprising a coprecipitate of manganese oxides and zirconia. Preferred catalysts are reduced.
The above compositions can be applied by coating to at least one atmosphere contacting (e.g., vehicle) surface. Particularly preferred compositions catalyze the destruction of ozone, carbon monoxide and/or unsaturated low molecular weight olefinic compounds at ambient conditions or ambient operating conditions.
Various of the catalyst compositions can be combined, and a combined coating applied to the atmosphere contacting surface. Alternatively, different surfaces or different parts of the same surface can be coated with different catalyst compositions.
The method and apparatus of the present invention are preferably designed so that the pollutants can be treated at ambient conditions, requiring no heating means or incidental heat. The present invention is particularly useful for treating ozone by coating a surface (e.g., motor vehicle atmosphere contacting surfaces) with suitable catalysts useful to destroy such pollutants at ambient conditions. The percent conversion of a pollutant, such as ozone depends on the temperature and space velocity of the atmospheric air relative to the catalyst surface, and the temperature of the atmosphere contacting surface.
Accordingly, the present invention, in its most preferred embodiments results in at least reducing the ozone levels present in the atmosphere without the addition of any mechanical features or energy source to existing substrates, particularly motor vehicles. Additionally, the catalytic reaction of ozone to oxygen takes place at the normal ambient conditions experienced by the surfaces of these motor vehicle elements when not in operation so that minimal changes in the construction or method of operation of the motor vehicle are required.
While the preferred embodiments of the present invention are directed to the destruction of pollutants at the ambient operating temperatures, it will be noted that the ambient air may be heated by a heating means such as a heater or by incidental or other contact with a heated component of the stationary substrate (e.g., the engine of a motor vehicle). This may allow other pollutants to be catalyzed which require a higher reaction temperature than the ambient temperature or ambient operating temperature of the atmosphere contacting surface. Such pollutants include carbon monoxide, hydrocarbons and nitrogen oxides. These pollutants can be treated at higher temperatures typically in the range of at least 40xc2x0 C. to 450xc2x0 C. This can be accomplished, for example, by the use of an auxiliary heated catalyzed surface. By an auxiliary heated surface, it is meant that there are supplemental means to heat the surface. A preferred auxiliary heated surface is the surface of an electrically heated catalyzed monolith such as an electrically heated catalyzed metal honeycomb of the type known to those skilled in the art. Electricity can be provided by batteries or a generator such as are present in motor vehicles. The catalyst composition can be any well known oxidation and/or reduction catalyst, preferably a three way catalyst (TWC) comprising precious group metals such as platinum, palladium, rhodium and the like supported on refractory oxide supports.
As previously stated, adsorption compositions can also be used to adsorb pollutants such as hydrocarbons and/or particulate matter for later oxidation or subsequent removal. Useful and preferred adsorption compositions include zeolites, other molecular sieves, carbon, and Group IIA alkaline earth metal oxides such as calcium oxide. Hydrocarbons and particulate matter can be adsorbed from 0xc2x0 C. to 110xc2x0 C. and subsequently treated by desorption followed by catalytic reaction or incineration.
It is preferred to coat areas of the substrate that have a relatively high surface area exposed to a large flow rate of atmospheric air. For land use motor vehicles, particularly preferred atmosphere contacting surfaces include the radiator, fan blades, the air conditioning condenser or heat exchanger, air charge cooler, engine oil cooler, transmission oil cooler, and wind deflectors of the type used on the roof of truck cabs.
Most preferably for motor vehicles, the atmosphere contacting surface is a surface of a radiator. The radiator has a large surface area for enhanced cooling of internal combustion engine fluid coolants. By applying a catalyst to be supported on the radiator surface, advantage can be taken of the large honeycomb-like surface area. The high honeycomb-like surface area enables a maximization of contact of the catalyst with the air passing through the honeycomb-like design of the radiator.
The present invention includes methods to coat pollutant treating compositions on to atmosphere contacting surfaces as described herein. In particular, the present invention includes a method to coat catalyst compositions onto finned elements such as radiators, air conditioner condensers, air charge coolers and other surfaces.